First detection of the 448 GHz H<SUB>2</SUB>O transition in space

DOI: 
10.1051/0004-6361/201730851
Publication date: 
01/04/2017
Main author: 
Pereira-Santaella, M.
IAA authors: 
Cazzoli, S.
Authors: 
Pereira-Santaella, M.;González-Alfonso, E.;Usero, A.;García-Burillo, S.;Martín-Pintado, J.;Colina, L.;Alonso-Herrero, A.;Arribas, S.;Cazzoli, S.;Rico, F.;Rigopoulou, D.;Storchi Bergmann, T.
Journal: 
Astronomy and Astrophysics
Refereed: 
Yes
Publication type: 
Article
Volume: 
601
Pages: 
L3
Abstract: 

We present the first detection of the ortho-H<SUB>2</SUB>O 4<SUB>23</SUB> - 3<SUB>30</SUB> transition at 448 GHz in space. We observed this transition in the local (z = 0.010) luminous infrared (IR) galaxy ESO 320-G030 (IRAS F11506-3851) using the Atacama Large Millimeter/submillimeter Array (ALMA). The water 4<SUB>23</SUB> - 3<SUB>30</SUB> emission, which originates in the highly obscured nucleus of this galaxy, is spatially resolved over a region of 65 pc in diameter and shows a regular rotation pattern compatible with the global molecular and ionized gas kinematics. The line profile is symmetric and well fitted by a Gaussian with an integrated flux of 37.0 ± 0.7 Jy km s<SUP>-1</SUP>. Models predict this water transition as a potential collisionally excited maser transition. On the contrary, in this galaxy, we find that the 4<SUB>23</SUB> - 3<SUB>30</SUB> emission is primarily excited by the intense far-IR radiation field present in its nucleus. According to our modeling, this transition is a probe of deeply buried galaxy nuclei thanks to the high dust optical depths (τ<SUB>100μm</SUB>〉 1, N<SUB>H</SUB>〉 10<SUP>24</SUP> cm<SUP>-2</SUP>) required to efficiently excite it.

Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018773484&doi=10.1051%2f0004-6361%2f201730851&partnerID=40&md5=4fe489532054447ee0c09c4483e3315a
ADS Bibcode: 
2017A&A...601L...3P
Keywords: 
galaxies: ISM;galaxies: nuclei;infrared: galaxies;ISM: molecules;Astrophysics - Astrophysics of Galaxies